Instant Messenger (hereinafter referred to as IM) is Internet-based communication service. IM enables the communication and interaction of texts, voice, videos, files and other information between the communicating parties. In general, after a user logs into the IM server with the user's account information through a caller terminal (e.g., a smartphone or tablet computer), the caller terminal user can make voice communication with the user of a callee terminal (e.g., another smartphone or tablet computer) that has already logged into the IM server to effectively save the economic costs of the two communicating parties.
However, in practice, both the caller and the callee terminals are requested to log into the IM server by the above-mentioned voice communication method. In terms of the callee terminals such as an old version of mobile phone without the capability to log into the IM server (e.g., a feature phone), the caller terminal cannot start voice communication via the IM server with the callee terminals even if the caller terminal logs into the IM server.